The present invention relates to pressure regulators, particularly to pressure regulators for tank pressurization, and more particularly to a pressure reducing regulator using a differential area piston arrangement with the outlet pressure referenced to a fraction of the inlet pressure.
Pressure regulators of various types have been developed for numerous applications. Pressure regulators typically use either a spring or a diaphragm pressurized by a sealed chamber to provide a reference pressure. However, the reference pressure would change with temperature, since springs can lose their temper when heated, and gas in a sealed chamber would exert more pressure on the diaphragm when heated.
In recent years substantial research and development have been directed to applications, such as propulsion systems, which utilize low propellant tank pressure to reduce the weight of the propellant tanks. Although the propellant tank pressure is low, a source of pressurant gas is required to maintain tank pressure as liquid is used, to expel the liquid at low pressure into the pumps which supply the propellant to the thrust chamber. Previous alternatives considered were (1) a small gas storage bottle with a cold gas regulator, (2) tank blowdown pressurization (e.g. fill the tank only 3/4 full and start with 4 times the required pressure), or (3) a substance in liquid-vapor equilibrium which boils to keep the tank at operating pressure as liquid is used therefrom. The first alternative results in increased weight of the tank because high pressure gas storage requires heavier material to withstand the internal pressure. The second alternative uses the tank volume inefficiently and requires a higher pressure capability for the tank. With the third alternative, the tank pressure depends on its temperature, so that it may be over pressurized if it becomes too warm (e.g. temperature extremes during storage).
The above problems relative to lower pressure tanks, particularly low pressure propellant tanks, such as those utilized in U.S. Pat. No. 5,026,259 issued Jun. 25, 1991 to J. C. Whitehead et al., and No. 5,222,873 issued Jun. 29, 1993 to J. C. Whitehead et al., which utilize reciprocating pump-fed rocket propulsion systems, are solved by the present invention and thus enables the operation of the propellant tank at a much lower pressure than the thrust chamber, in order to achieve high performance by using lightweight tankage. The present invention solves the above problem by using a small amount of the high pressure, high temperature gas which is used to power the pumps on the propulsion system, such as those of the above-referenced U.S. Patents.